Copper-iron alloy



April 30, 19353. Q 5 SMlTH'Er AL 1,999,850

COPPER IRON ALLOY n Filed DSC. 20, 1934 BdS ltd/M5595 '7600GT/01V 'FFECTUFMA w/A/G avomr/fs @FA COPPER-/Ra/v-MAGA/Fs/z/M met (g2- Cu ANCE ALL 7537's O/v 0.040 Ml. w/A. e

l INVENTOR;

Patented Apr. 30, 1935 UNITED STAT-Es PATENT c' oFFlcE COPPER-IRON Armor Application December 20, 1934, Serial No. 758,442

1s Claims.

Our invention relates to an improved copperiron alloy having a high strength combined with a high electrical conductivity, and capable of 'being severely worked, as for example beingdrawn 5 into fine wire.

The figure of the drawing shows a set of curves indicating the effect of drawing on certain properties of an example of our new alloy.

The earliest literature (Stead-Journ. Iron and Steel Institute, 1901, 60, 104; Sahmen-Z. Anorg. Chem. 1908, 57, 1; and Burgess and Aston-Trans. Amer. Elec. Chem. Soc. 1909, 16, 24) states that the metals copper and iron are miscible in all proportions the liquid state, although not in the solid state. Later Ruer and his collaborators (Ferrum 1913, 11, 39 and 1916, 14, 49) published an equilibrium diagram showing incomplete miscibility in the liquid-state, although their diagram is not thermodynamically correct. The investigations of Muller (Z. Anorg. Chem. 1927, 162, 231) suggested that there was a closed miscibility gap in the -iron-copper system, similar to that found insome organic systems, whichv did not intersect the liquidus but which left a zone vsome 50 wide wherein the metals were miscible at all compositions. Additions of carbon were found to depress the two-liquid zone until it intersected the liquidus and a homogeneous liquid was not obtainable in the range'30 to 80 percent copper at any temperature.

In our experiments we have found it possible to make homogeneous melts of alloys of copper and iron in any proportion whatsoever and at any temperature above the liqudus up to about 1700 C. and probably higher. We found, however, that the presence of a. small amount of carbon, about 0.13 per cent in the 50 per cent alloy or less with higher copper, produces separation into two liquids and the discrepancy in the earlier work is undoubtedly due to impurities such as carbon. We have found that silicon and chromium tend to decrease miscibility while manganese and nickel seem to improve it. l

Without exception the ,published works state that it is impossible to forge an alloy containing from 7 to 80 percent copper. We have found that ternary alloys of copper, iron and magnesium containing small amounts of magnesium may be forged and even hot rolled with severe passes. These alloys are not diiiicult to forge or roll except in the range of approximately 8 to 30 percent copper, but even these latter alloys can be rolled at a temperature not exceeding about 845 C. (the eutectoid temperature) after an annealing treatment at about 800 C. which leaves (Cl. 14S-11.5)

the alloy in the softest possible condition. The alloys containing approximately 10 percent copper are the strongest in the series and show very attractive mechanical properties when quenched from above the eutectoid temperature and reheated at about 400 C., but when a high electrical conductivity is required the presence of a larger amount of copper is necessary. The alloys in the range to 90 percent copper are difcult to cast on account of the great difference between the pouring temperature and the final solidication point.

composition from 10 to 80 percent copper it is necessary to employ a smooth mold so that the ingot 'can contract freely, otherwise it will develop internal cracks on account of the long range of temperature in which it is hot-short.

The alloys containing approximately 30 to 70 percent copper, 0.02 to l percent magnesium and balance iron are easy to cast and may be severely rolled at any temperature up to 1050 C. with no preliminary treatment. While the conductivity increases roughly in proportion to the increase in copper content, the tensile. strength decreases. The most desirable combination of strength and conductivity occurs in the range of approximately 50 to 60 percent copper with magnesium from approximately 0.02 to I per.

cent and balance iron. If in some applications it `becomes desirable to sacrifice some conductivity for additional strength the copper may be decreased with corresponding increase in iron. If high conductivity ismore important than high strength the copper content may be increased.

The smallest amount of magnesium that is effective in improving the forging qualities is about 0.02 percent. We prefer to use about 0.20 percent magnesium and the amount may be as high as 1 percent. The magnesium is added' to the molten copper-iron alloy either as the4 element or preferably as a magnesium-copper a1- loy although other magnesium containing alloys may be used. Some loss of magnesium oc- In casting the alloys of any a particular disadvantage.

'72,000 lbs. per square inch. After rolling and annealing this becomes 80,000 lbs. per square inch, but cold working such as drawing or rolling increases the strength to as much as 170,000 lbs. per lsquare inch without severe loss in' ductility and without decreasing the conductivity very much. This is clearly shown in the drawing wherein are plotted the properties of an alloy containing 56 percent copper and 0.21 percent magnesium drawn from annealed wires at various sizes to a constant nishing size of 0.040 inch.

To obtain the maximum electrical Aconductivity it is necessary to anneal the alloy and slowly cool it in order to precipitate as much iron as possible from solid solution in the copper and as much copper as possible from the iron. If. as is usually the case, the alloy has been hot or cold rolled from the casting to the form of a rod or other intermediate shape, heating at a temperature of about 600 to 850 C. is necessary in order to relieve cold work and cause recrystallization and softening of the alloy prior to the final cold drawing, but this results in rather poor conductivity (about 22 percent I. A. C. S.) The preferred treatment is at about 700 C. for about one hour. If the alloy, after this treatment, is given a long annealing (about 72 hours) at about 500 C. the conductivity will increase to about 42 percent I. A. C. S., but the most rapid treatment for improving the conductivity consists of slowly cooling the alloy through the approximate range of 600 to 450 C., preferably in a time of about 2 hours, although a longer time will give higher conductivity and a shorter cooling time (not under about 30 minutes) may be used under some conditions. Any method of cooling from about 450 C. at the termination of this treatment may be employed without material effect on the properties. This annealing and cooling treatment in an alloy containing about 55 percent copper and 0.2 percent magnesium results in a conductivity of about 41 percent I. A. C. S. and leaves the alloy in the softest possible condition. Subsequent drawing increases the tensile strength, as shown in the drawing and slightly decreases the conductivity, although Vthe wire drawn eleven B & S numbers reduction has a tensile strength of 164,000 lbs. per square inch and a conductivity of over 35 percent I. A. C.` S. This combination of strength and conductivity is unapproached so far as we are aware by any other alloy.

On account of thefthin layer of copper produced on thesurface of the alloy by pickling, (which may be done in any of the usual solutions, though we prefer hot 10 percent sulphuric acid) the wire is easy to draw and does not cause excessive die wear in spite of its high strength.

The alloy is useful not only in the form of wire, which is probably its principal application, but also as strip, forgings, castings or other forms. The corrosion resistance of the alloy is not good compared with many copper alloys, but there are many applications where this is not The alloys should be useful for springs where high conductivity is required, and its comparative hardness and high conductivityis useful for electrodes for resistance welding machines of various types.

Having thus set forth the nature of our invention, what we claim is:

1.An alloy comprising approximately 30 to 70 percent copper, 0.02 to 1.0 percent magnesium, and balance iron.

2. An alloy comprising approximately to 6'0 percent copper', 0.02 to 1.0 percent magnesium and balance iron.

3. An alloy comprising approximately percent copper, 0.2 percent magnesium, and balance iron.

4. A wrought metal article composed of an alloy comprising approximately 30 to 70 percent copper, 0.02 to 1.0 percent magnesium, and balance iron.

5. A wrought metal article composed of an alloy comprising approximately 50 to 60 percent copper, 0.02 to 1.0 percent magnesium, and balance iron.

6. A wrought metal article composed of an `alloy comprising approximately 55 percent copper, 0.2 percent magnesium, and balance iron.

7. A cold drawn wire composed of an alloy of approximately 30 to 70 percent copper, 0.02 to 1.0 percent magnesium, and balance iron.

8. A cold drawn wire composed of an alloy of approximately 50 to 60 percent copper, 0.02 to 1.0 percent magnesium, and balance iron.

9. A cold drawn wire composed of an alloy of approximately 55 per cent copper, 0.2 percent magnesium, and balance iron.

10. A cold drawn wire characterized by high strength and high electrical conductivity fabricated from an alloy containing approximately 30 Vto 70 percent copper, 0.02 to 1.0 percent magnesium and balance iron, which alloy prior to the last drawing had been rolled and given an anneal at 600 to 850 C. for from 1A, to 4 hours followed by slow cooling through the range 600 to 450 C. in about 1/2 to 8 hours, and cooled to approximately room temperature.

11. A'cold drawn wire characterized by high strength and high electrical conductivity fabricated from an alloy containing approximately 50 to 60 percent copper, 0.02 to 1.0 percent magnesium and balance iron, which alloy prior to the last drawing had been heated to between 600 to 850 C. to anneal it, and then maintained at a temperature of approximately 500 C. for a sumcient time to substantially increase the electrical conductivity.

12. A cold drawn wire characterized by high strength and high electrical conductivity composed of an alloy of approximately 55 percent copper, 0.2 percent magnesium and balance iron, which alloy prior to the finishing by cold drawing was annealed for about one hour at approximately 700 C. and slowly cooled through the range 600 to 450 C. in about 2 hours.

13. A method of increasing the strength and electrical conductivity of an alloy composed of approximately 30 to 70 percent copper, 0.02 to 1 percent magnesium, and balance iron, which comprises heating the alloy to between 600 to 850 C., cooling slowly through the approximate range of 600 to 450 C., and then cold working.

' 14. A method of increasing the strength and electrical conductivity of an alloy composed of approximately 30 to '70 percent copper, 0.02 to 1 percent magnesium, and balance iron, which comprises heating the alloy to between 600 to 850 C., then maintaining it at a temperature of approximately 500 C. for suicient time to substantially increase the electrical conductivity, and then cold working.

15. A method of increasing the strength and electrical conductivity of an alloy composed of approximately 50 to 60 percent copper, 0.02 to 1 percent magnesium, and balance iron, which comprises heating the alloy to between 600 to 850 C.,

cooling slowly through the approximate range of 600 to 450 C., and then cold Working.

16. A method of increasing the strength and electrical conductivity of an alloy composed of approximately 50 to 60 percent copper, 0.02 to 1 percent magnesium, and balance iron, which comprises heating the alloy to between 600 and 850c C., then maintaining it at a temperature of approximately 500 C. for sufcient time to sub stantially increase the electrical conductivity, and then cold working. y

17. A method of increasing the strength and electrical conductivity of an alloy composed of approximately 55 percent copper, 0.2 percent magnesium, and balance iron, which comprises heating the alloy to between 600 to 850 C., cooling slowly through the approximate range of 600 to 450 C., and then cold working.

18. A method of increasing the strength and electrical conductivity of an alloy composed of approximately 55 percent copper, 0.2 percent magnesium, and balance iron, which comprises heating the alloy to between 600 and 850 C., then maintaining it at a temperature of approximately 500 C. for sufficient time to substantially increase the electrical conductivity, and then cold working.

CYRIL STANLEY SMITH. EARL W. PALMER. 

